This pilot randomized double-blind, placebo-controlled clinical trial addresses the controversy over whether or not dietary multivitamin/mineral supplements should be taken during radiotherapy for cancer. Although there is considerable in vitro evidence supporting the use of antioxidant vitamins during cancer treatment, studies testing the effects in cancer patients are very limited. The current lack of evidence to guide health care providers, who are on the clinical front lines of nutritional symptom management for patients with cancer, becomes more critical as increasing numbers of Americans with cancer are taking multivitamin supplements as self-care strategies. The purpose of the study is to determine the effects of two commonly used dosages of dietary multivitamin/mineral supplements by individuals with prostate-cancer receiving radiotherapy. This is NOT a dose response study. Rather the purpose is to determine the effects on treatment outcomes of common dosages of self-therapy with dietary nutritional supplements used by cancer patients. Two standardized regimens of multivitamin/mineral supplements will be compared to a placebo. The dosages will be at: (1) dietary reference intake levels for optimal health (DRI regimen) and (2) orthomolecular levels for antioxidants (orthomolecular regimen). The specific aims are to: (1) determine the effects of two nutritional supplement regimens (DRI and orthomolecular) on localized tumor response to radiation therapy and (2) determine the effects of two nutritional supplement regimens on nutritional status and the resulting systemic changes in oxidative damage, immune function, radiation side effect severity, and quality of life. This study will provide pilot and feasibility evidence for a larger scale clinical trial as well as evidence for health care providers and individuals with cancer regarding the use of multivitamins and antioxidants during radiation treatment. The application is submitted in response to PA-04-053 Developmental Projects in Complementary Approaches to Cancer Care because little is known about the effects of this self-care strategy on cancer treatment efficacy. [unreadable] [unreadable]